It is my understanding that when you have Medicare Advantage, also know as a Medicare Part C plan, it subsumes both Part A and Part B for plan participants. I think of this role as providing an umbrella under which Parts A(hospitalization), B ( doctors and outpatient treatment,) and often Part D (medication not covered under Part B) are administered.

Although an Advantage Plan must provide the same benefits as Medicare Parts A& B, I think it can play around a bit with the procedure for obtaining those benefits. For example, the expanding trend of prior approval might be just that sort of 'playing around.'

I thought I could provide a cite to where I read this on one of the Medicare.gov myriad websites, but cannot locate it now.